zephyr/Kconfig: not use cc310 by default

Usage of cc310 by defaults gives poor user
experience out of the box as it requires manual
cloning of nrfxlib repository.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index ec56dc2..05c7c10 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -68,7 +68,6 @@
 
 choice
 	prompt "Signature type"
-	default BOOT_SIGNATURE_TYPE_ECDSA_P256 if HAS_HW_NRF_CC310
 	default BOOT_SIGNATURE_TYPE_RSA
 
 config BOOT_SIGNATURE_TYPE_NONE
@@ -93,7 +92,6 @@
 if BOOT_SIGNATURE_TYPE_ECDSA_P256
 choice
 	prompt "Ecdsa implementation"
-	default BOOT_ECDSA_CC310 if HAS_HW_NRF_CC310
 	default BOOT_ECDSA_TINYCRYPT
 
 config BOOT_ECDSA_TINYCRYPT